<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8">
        <title>HTML5</title>
        <style>
            body{
                background-color: #aaa;
            }
            div{
                border:1px solid #000;
                text-align: center;
                background-color: #fff;
            }
            #header{
                width:100%;
                margin:0 auto;
                margin-bottom:10px;
            }
            #nav{
                width:100%;
                margin:0 auto;
                margin-bottom:10px;
            }
            .section{
                width:100%;
                margin:0 auto;
                background-color: #eee;
                margin-bottom:10px;
            }
            .article{
                width:60%;
                height:500px;
                display:inline-block;
                vertical-align: top;
            }
            .sidebar{
                width:35%;
                height:500px;
                display:inline-block;
                vertical-align: top;
            }
            #footer{
                width:100%;
                margin:0 auto;
                height:60px;
                clear: both;
            }
        </style>
    </head>
    <body>
        <div id="header">
            &lt;div id="header"&gt;
        </div>
        <div id="nav">
            &lt;div id="nav"&gt;
        </div>
        <div class="section">
            &lt;div class="section"&gt;
            <br>
            <div class="article">
                &lt;div class="article"&gt;
            </div>
            <div class="sidebar">
                &lt;div class="sidebar"&gt;
            </div>
        </div>
        <div id="footer">
            &lt;div id="footer"&gt;
        </div>
    </body>
</html>